T cell dysfunction contributes to the susceptibility of patients with the Wiskott-Aldrich syndrome (WAS) to infection, autoimmunity and lymphoid malignancy. This project probes the function of WASP and its partner WASP interacting protein WIP in T cells. Most of WASP is complexed with WIP in T cells. WASP levels of drop to ~10% of normal in T cells from WIP KO mice and from WAS patients with mutations that disrupt WIP binding, suggesting that WIP stabilizes WASP. Our Preliminary data show that the hierarchy of T cell dysfunction is WASP/WIP DKO>WIP KO>WASP KO, bearing in mind that since WASP levels are low in WIP KO T cells the individual contribution of WIP to the WIP KO phenotype is unknown. Our overall hypothesis is that WIP and WASP function in T cells both independently and as a complex. To test our hypothesis we propose to use genetically engineered mice which selectively lack WIP, WASP or both, or in which the WASP/WIP complex is disrupted. We will: 1. Compare T cell function in DKO mice and WASP KO mice in vitro and in vivo and probe the structure and function of the cytoskeleton of DKO and WASP KO T cells to test the hypothesis that WIP has functions that are independent of WASP. 2. Reconstitute T cells from WIP KO mice with the WASP binding domain (WBD) of WIP to generate T cells that are strictly WIP deficient. We will compare these strictly WIP deficient T cells to DKO T cells to define WASP functions that are independent of WIP. 3. Disrupt the WASP/WIP complex expressing the WBD in WT T cells to test the hypothesis that there is a subset of signaling functions that is dependent on the WASP/WIP complex. 4. Generate and analyze T cells that express a WIP mutant that lacks the actin-binding region to determine the role of the recruitment of the WIP/WASP complex to actin in T cell function. The results of the proposed experiments in the mouse will aid in our understanding of the pathogenesis of WAS in humans and should lead to novel treatments for this disease. [unreadable] [unreadable] PUBLIC HEALTH RELEVANCE: Wiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency due to mutations in the WASP gene and is characterized by recurrent infections, thrombocytopenia and eczema. T cell dysfunction contributes to the susceptibility of patients with the Wiskott- Aldrich syndrome (WAS) to infection, autoimmunity and lymphoid malignancy. This project probes the function of WASP and its partner WASP interacting protein WIP in T cells. Our overall hypothesis is that WIP and WASP function in T cells both independently and as a complex. Defining these functions is central in understanding the molecular pathology of WAS. The results of the proposed experiments in the mouse will aid in our understanding of the pathogenesis of WAS in humans and should lead to novel treatments for this disease. [unreadable] [unreadable] [unreadable]